[Paper Review] Geometric and electronic properties of graphene-related systems: Chemical bondings

Ngoc Thanh Thuy Tran, Shih-Yang Lin+2 more|arXiv (Cornell University)|Feb 6, 2017

Fullerene Chemistry and Applications4 citations

TL;DR

This first-principles study systematically investigates how geometric and electronic properties of graphene-related systems are tuned by layer number, stacking order, strain, ripples, and adatom doping. It reveals that multi-orbital chemical bonding—especially from H, F, O, halogens, alkali metals, and Al adatoms—induces tunable energy gaps, Dirac cone reconstruction, and emergent magnetic or metallic behavior, enabling design of functional 2D nanomaterials for electronics and energy applications.

ABSTRACT

This work presents a systematic review of the feature-rich essential properties in graphene-related systems using the first-principles method. The geometric and electronic properties are greatly diversified by the number of layers, the stacking configurations, the sliding-created configuration transformation, the rippled structures, and the distinct adatom adsorptions. The top-site adsorptions can induce the significantly buckled structures, especially for hydrogen and fluorine adatoms. The electronic structures consist of the carbon-, adatom- and (carbon, adatom)-dominated energy bands. There exist the linear, parabolic, partially flat, sombrero-shaped and oscillatory band, accompanied with various kinds of critical points. The semi-metallic or semiconducting behaviors of graphene systems are dramatically changed by the multi- or single-orbital chemical bondings between carbons and adatoms. Graphene oxides and hydrogenated graphenes possess the tunable energy gaps. Fluorinated graphenes might be semiconductors or hole-doped metals, while other halogenated systems belong to the latter. Alkali- and Al-doped graphenes exhibit the high-density free electrons in the preserved Dirac cones. The ferromagnetic spin configuration is revealed in hydrogenated and halogenated graphenes under certain distributions. Specifically, Bi nano-structures are formed by the interactions between monolayer graphene and buffer layer. Structure and adatom-enriched essential properties are compared with the measured results, and potential applications are also discussed.

Motivation & Objective

• To systematically map the geometric and electronic properties of graphene-related systems across diverse structural and chemical configurations.
• To understand how multi-orbital chemical bonding between carbon and adatoms (e.g., H, F, O, halogens, alkali metals, Al) alters electronic band structures and energy gaps.
• To correlate structural features—such as stacking order (ABA, ABC, AAA), ripples, and sliding configurations—with emergent electronic behaviors including semimetallicity, semiconducting gaps, and metallic states.
• To explore spin-polarized configurations in hydrogenated and halogenated graphenes, identifying conditions for ferromagnetism.
• To link theoretical predictions with experimental measurements (e.g., ARPES, STM, STS) and assess the potential of doped graphenes in functional nanodevices.

Proposed method

• Employing first-principles density functional theory (DFT) calculations to model pristine, doped, and functionalized graphene systems.
• Analyzing orbital hybridizations (sp², sp³, p-d, etc.) and their impact on electronic band dispersions and density of states (DOS).
• Investigating stacking configurations (ABA, ABC, AAA, AAB) and their influence on interlayer coupling and energy band topology.
• Simulating adatom adsorption at top, bridge, and hollow sites to assess structural buckling and charge redistribution.
• Using tight-binding models and band structure analysis to interpret linear, parabolic, flat, sombrero-shaped, and oscillatory bands.
• Comparing theoretical results with experimental data from ARPES, STM, STS, and optical/electrical measurements.

Experimental results

Research questions

• RQ1 How do stacking configurations (e.g., ABA, ABC, AAA) influence the electronic band structure and Dirac cone integrity in few-layer graphenes?
• RQ2 What role do multi-orbital chemical bonds (e.g., C–H, C–F, C–O, C–Al) play in inducing energy gaps and modifying semimetallic behavior?
• RQ3 Under what conditions do hydrogenated and halogenated graphenes exhibit ferromagnetic spin ordering?
• RQ4 How do ripples and strain affect the local electronic structure and charge density distribution in graphene?
• RQ5 To what extent can alkali- and Al-doping enhance free electron density while preserving Dirac cone features?

Key findings

• Top-site adsorption of H and F induces significant structural buckling due to strong p–p hybridization, altering the planar geometry.
• Fluorinated graphenes exhibit semiconducting or hole-doped metallic behavior depending on fluorine coverage and configuration.
• Hydrogenated and halogenated graphenes can display ferromagnetic spin configurations under specific adatom distributions, as supported by spin-polarized STS.
• Alkali- and Al-doped graphenes maintain Dirac cones with high-density free electrons, indicating potential for high-mobility electronic devices.
• Graphene oxides show tunable energy gaps ranging from insulating to semimetallic, depending on oxygen functionalization patterns.
• Bi-doped systems form nanostructures via interaction with the buffer layer, leading to distinct low-energy DOS features and potential for spintronic applications.